Electrophotographic coating compositions having bromine-containing polymer binders

ABSTRACT

PHOTOCONDUCTIVE COATING COMPOSITIONS FOR APPLICATION TO SOLID SUBSTRATES WHICH ARE TO BE UTILIZED IN ELECTROPHOTOGRAPHIC OPERATIONS ARE DESCRIBED; THE RESULTANT PHOTOCONDUCTIVE COATINGS COMPRISE A LAYER OF PHOTOCONDUCTIVE PIGMENT PARTICLES BONDED TO THEMSELVES AND TO THE SOLID SUBSTRATE WITH A BINDER COMPRISING A NOVEL INTERPOLYMER, AT LEAST ONE OF WHOSE CONSTITUENT MONOMERS CONTAINS BROMINE. NOVEL BROMINE-CONTAINING MONOMERS ARE ALSO DISCLOSED.

United States Patent ELECTROPHOTOGRAPHIC COATING COMPOSI- TIONS HAVINGBROMINE-CONTAINING POLY- MER BINDERS Dilip K. Ray-Chaudhuri, Somerville,Paul C. Georgoudis, Dunellen, and Hans H. Stockmann, Plainfield, N.J.,assignors to National Starch and Chemical Corporation, New York, N.Y. NoDrawing. Filed Aug. 4, 1971, Ser. No. 169,075

Int. Cl. C08f /00, 15/16 U.S. Cl. 260-47 UA 3 Claims ABSTRACT OF THEDISCLOSURE Photoconductive coating compositions for application to solidsubstrates which are to be utilized in electrophotographic operationsare described; the resultant photoconductive coatings comprise a layerof photoconductive pigment particles bonded to themselves and to thesolid substrate with a binder comprising a novel interpolymer, at leastone of whose constituent monomers contains bromine. Novelbromine-containing monomers are also disclosed.

BACKGROUND OF THE INVENTION This invention relates to newphotoconductive coating compositions, and more particularly to suchcompositions comprising polymeric binders derived from brominecontainingmonomers and to the improved photoconductive coatings prepared from suchcompositions.

In the known electrophotographic processes, a solid substrate which hasbeen coated with a photoconductive surface is electrostatically chargedin the absence of light. The charged surface is then exposed to a lightsource, such as an image reflected from a printed surface or transmittedthrough a transparency, which serves to discharge the exposed area whilehaving no effect upon the charge on the unexposed areas which is thusretained in the form of an electrostatic image. The surface areas arethen contacted with an electrostatically charged marking powder ordispersion which clings to the charged areas but does not adhere to theuncharged, i.e. exposed, areas. The visible image which is thus formedmay then be transferred to another surface resulting in a positive ornegative print, or, if desired, it may be fused in order to fix theimage directly to the solid substrate itself.

It is evident that the proper selection of a photoconductive system isessential for a successful electrophotographic operation. Among theproperties that must be exhibited by such photoconductive materials areincluded: the ability to accept an electrostatic charge; the ability tohold the charge for a period of time in the absence of light withoutexhibiting a rapid rate of charge decay; the ability to provide thefixed or developed sheets with excellent print density; the ability toprovide an efiicient dispersing medium for the pigment particles;inertness of the binder toward the pigment which is being utilized; and,the ability to be readily coated on a solid substrate.

A frequently utilized photoconductive system comprises the combinationof a zinc oxide pigment and polyvinyl acetate or a styrene interpolymerbinder. These systems, however, do not exhibit the aforementionedproperties to an optimum level.

It is recognized in the art that the properties of anelectrophotoconductive system are realized not only from the particularphotoconductive pigment which is utilized; rather, it is the combinationof the pigment with a particular binding agent which is the criticalfactor. It can be understood, therefore, that the choice of a bindingagent in connection with a pigment, such as zinc oxide,

3,793,293 Patented Feb. 19, 1974' charbonded with a binding agentcomprised of an interpolymer derived from at least onebromine-containing monomer realize the above described requirements forachieve ing an elfective electrophotographic system having desirablecharacteristics. A particular feature of the presentelectrophotoconductive compositions is their ability to discharge theirelectrostatic charge almost instantaneously in the presence of light.Thus, we have found that solid substrates which have been coated withthe latter material will accept and hold an electrostatic charge in theabsence of light, and upon being exposed to light will immediatelyrelease the charge from the exposedareas but will retain the charge onthe unexposed areas with a high degree of efliciency and for a period oftime sufficient to permit visible development of the electrostatic imageformed by the unexposed areas. Furthermore,

these photoconductive systems are readily coated onto a variety of solidsubstrates and provide the resulting printed sheet with excellentdensity, i.e. with excellent definition of the visible image.

SUMMARY OF THE INVENTION plates for use in electrophotographicoperationsby coating the latter photoconductive system onto applicable solidsubstrates. Various other objects and advantages of this invention willbe apparent from the following description thereof.

The polymeric binder system which is utilized in conjunction with thephotoconductive pigment serves to bind the particles of the latterpigment to themselves as well as to the selected substrate. It therebyplaces these pigment particles in a spatial relationship with oneanother such that they are rendered photoconductive in those areas inwhich light radiation strikes the coating.

The novel binders of this invention are interpolymers comprised ofresidues derived from at least one brominecontaining monomer selectedfrom the group consisting of compounds of the following generalformulas:

(e) Br R1-=H, 01' CH3, R =a1ky1 radical having 1 to 4 carbon atoms,R3=H, CH3, 01' 'CH2Bl',

and at least one monomer which does not contain bromine selected fromthe group consisting of monomers having the following general formulas:

R =H, C1, or t-butyl,

R =an alkyl radical of 1 to 8 carbon atoms or a cycloalkyl radical of 3to 8 carbon atoms, and

then be used in the form of the organic solutions in which they wereoriginally prepared. Alternatively, they may be prepared as 100% resinsolid materials, as by means of a bulk or pearl polymerizationprocedure, and subsequently dissolved in organic solvents prior to theiruse as binders-in our photoconductive coating composition. Theseinterpolymers may also be prepared using emulsion polymerizationtechniques well known to those skilled in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although all of thebromine-containing monomers listed above are useful in preparing theimproved binders of this invention the following monomers are preferred:2-bromoethyl methacrylate, 2-bromoethyl maleate,ethyleneglycolmonomaleate 2 carboethoxy-3,4,5,6-tetrabromobenzoate,propyleneglycolmonomaleate 2 carboethoxy-3,4,5-tetrabromobenzoate,ethyleneglycolmonomaleate-2-carbobutoxy-3,4,5,6-tetrabromobenzoate, andpropyleneglycolmonomaleate 2 carbobutoxy 3,4,5,6-tetrabromobenzoate.

Of the monomers useful in preparing the novel polymers of this inventionthose of the types (a), (b), (c), (d), (e), and (f) are themselvesnovel.

Monomers of type (a) are prepared by the esterification of acrylic ormethacrylic acid with 2,-3-dibromoallyl alcohol following theconventional method of esterification. 2,3-dibromoa1lyl alcohol isprepared by adding 1 mole of bromine across the triple bond of propargylalcohol in chloroform at 5 to 15 C. The brominated alcohol is thendistilled under reduced pressure to obtain a pure product.

Monomers of type (b) are prepared by the reaction of 1 mole of maleicanhydride and 1 mole of 2,3-dibromoallyl alcohol at to C. using 0.1 to0.5% triethylamine or sodium acetate as a catalyst. The final product isalmost colorless viscous product having an acid number close to theory.

A typical monomer of the (0) type may be synthesized as follows in amixture with a monoalkyl maleate or in pure form. The monomer is easierto synthesize in a mixture with 50 mole percent of monoalkyl maleate. Itcan also be synthesized in 100% purity by isolating the intermediatehydroxyalkyl alkyl tetrabromophthalate from the mixture in the secondstep of the reaction shown below and then reacting it with maleicanhydride.

The synthesis of monomer mixed with monoalkyl maleate may be describedby the following sequence of reactions.

(1) Br CO Br Br Br COOR:

O 2R2OH R2011 Br Br COOH C0 Br Br Br 000R:

RzOH R1CH-CH2 Br COOH Br COOR RiOH Br -COOCHZ?HOH Bl R1 Br Br COOR2 3R2011 zil Br oooomonon H0O Br 000R,

Br Br ooocmon RzOOCCH=CHCOOH H (soon In the first reaction one mole oftetrabromophthalic anhydride is reacted with 2 moles of alkanol at 70 to100 C. for 2 to 4 hours to form one mole of monoalkyltetrabromophthalate and one mole of unreacted alkanol. In the secondstep this mixture is reacted with alpha olefin oxide such as ethyleneoxide and propylene oxide, at 70-100 C. in a closed reactor or atatmospheric pressure for 2 to 4 hours in the presence of 1 to 3% (basedon the mixture) tetramethylammonium chloride as a catalyst to form onemole of hydroxyalkyl alkyl tetrabromophthalate and one mole of unreactedalkanol. In the final step the above mixture is reacted with 2 moles ofmaleic anhydride at 70 to 100 C. to form one mole ofalkyleneglycolmonomaleate 2 carboalkoxy-3,4,5,-6-tetrabromobenzoate andone mole of monoalkylmaleate. The above monomer mixture is obtained as aslightly hazy, viscous liquid.

The 100% pure monomer is prepared by isolating the intermediate from themixture obtained in the second step. The unreacted alkanol is removed bydistillation under reduced pressure followed by washing the solution ofintermediate in aromatic hydrocarbon solvent with water. A higheralkanol such as butanol requires thorough washing with water due to itslow solubility in water. The washed intermediate is dried with a dryingagent, stripped of solvent under reduced pressure at 2550 C., and thenreacted with one mole of maleic anhydride to form a purealkyleneglycolmonomaleate-2-carboalkoxy-3,4,5,6- tetrabromobenzoate as aviscous liquid.

Monomers of type (d) are synthesized by the reaction of one mole oftetrabromophthalic anhydride and 1.25 to 2 moles hydroxyalkyl acrylateor hydroxyalkyl methacrylate at 80 to 100 C. for 3 to 6 hours using 1 to5% (based on total charge) triethyla-mine as a catalyst. The mixture isthen diluted with solvent (toluene, chloroform, methylenechloride, etc.)and washed with water several times to remove unreacted hydroxyalkylacrylate or methacrylate and triethylamine. The washed monomer is driedwith a drying agent (anhydrous sodium sulfate) and stripped of solventunder reduced pressure at 40-50 C. The finished monomer is obtained as aslightly colored viscous liquid having an acid number close to theory.

Monomers of type (e) are prepared by the reaction of2,4,6-tribromophenol with an alphaolefin oxide such as ethylene oxideand propylene oxide, in the presence of 1 to 3 percenttetramethylammonium chloride at 80 to 100 C. for 3 to 6 hours to form2,4,6-tribromophenoxyethanol. The reaction mixture is washed thoroughlywith water after dissolving in solvent, dried with a drying agent, andstripped of solvent under reduced pressure at 40 to 60 C. The product isthen analyzed for hydroxyl number. The yield of this intermediate isgenerally 40 to 60%. The intermediate is then reacted with maleicanhydride at to C. for 3 to 5 hours to form mono-2,4,6-tribromophenoxyethyl maleate.

The monomer is obtained as a slightly colored viscous liquid.

Monomers of type (f) can be synthesized using the same procedure as isused for monomers of type (e) by replacing tribromophenol withdibromophenol.

Preferred monomers which do not contain bromine and are useful inpreparing the photoconductive polymers of this invention are: styrene,dibutylfumarate, dibutylmaleate, ethylacrylate, butylacrylate,hydroxypropylmethacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxyethyl acrylate, vinylacetate, monoethylmaleate,monobutylmaleate, acrylic acid, methacrylic acid, and crotonic acid.

All of the interpolymers used in the binder compositions describedherein may be prepared by means of free radical intiated polymerizationprocedures or by other polymerization procedures well known to thoseskilled in the art. However, they are most conveniently prepared bymeans of free radical initiated solution polymerization techniques andthey may be then used in the form of the organic solvent solutions inwhich they were originally prepared. Alternatively, they may be preparedas 100% resin solids material, as by means of a bulk or pearlpolymerization procedure, and subsequently dissolved in organic solventsprior to their use as binders in our photoconductive coatingcompositions. Organic solvents which may be employed for the solutionpolymerization of these interpolymers as Well as for their ultimate usein formulating our photoconductive coating compositions include benzene,toluene, xylene, cyclohexane, ethyl acetate, isopropyl acetate, methylethyl ketone and methyl isobutyl ketone as Well as mixtures of any ofthe latter solvents. Typical organic solvent solutions of theseinterpolymers, as used in preparing our photoconductive coatingcompositions, should have a resin solids content of up to about 70%, byweight.

These interpolymers may also be prepared using emulsion polymerizationtechniques well known to those skilled in the art.

It is to be understood that although zinc oxide will ordinarily beutilized as the photoconductive pigment component of our novelcompositions, it may, however, be replaced with various equivalentstherefor, such for example, as titanium dioxide, selenium oxide, zincsulfide, and the like. Moreover, a mixture of more than onephotoconductive pigment may likewise be used.

The actual preparation of the novel photoconductive coating systems ofthis invention may be accomplished merely by admixing and dispersing thephotoconductive pigment in an organic solvent solution of the selectedinterpolymer and thereafter finely grinding the resulting dispersion inany suitable equipment, such as a porcelain ball mill, Morehouse mill,kady mill, or sand mill, to a pigment particle size of from about 4 to 6units on the Hegman scale.

Approximately from about 2 to 12 parts, by weight, of zinc oxide solidsshould be present in the mixture for each part, by Weight, of theinterpolymer resin solids. We have found that the total solids content,i.e. the combined weight of the pigment solids and the interpolymersolids, of our photoconductive coating compositions may vary from about30 to 60% by Weight. Appropriate dilution, when necessary, can be madeusing any one or more of the organic solvents described hereinabove.

The preparation is generally completed by incorporating a sensitizer dyeor dye mixture into the coating composition in a concentration rangingfrom about 0.02 to 0.50%, based on the weight of the zinc oxide.Applicable sensitizers include, for example, disodium fluorescein, RoseBengal, Bromphenol Blue, Methylene Blue, Briochrome Black, Eosin Y, andAcridine Orange. The addition of the latter sensitizers may, however, beobviated if the resulting photoconductive systems are to be utilized ina procedure whereby the light or energy source is itself capable ofcausing a conductive response in the zinc oxide photoconductive pigment.

Optional additives may be incorporated into these novel photoconductivesystems in order to modify certain properties thereof. Among suchadditives are included: plasticizers such as dialkyl phthalates; opticalbrighteners such as titanium dioxide; silicones; and, modifying resinssuch as alkyd resins.

Our novel systems may be coated onto a wide variety of solid substratessuch, for example, as paper, paperboard, fabrics made from natural andsynthetic fibers, metallic coated paper, metallic foils, and syntheticresinbased films such as polyethylene terephthalate, polyethylene,polypropylene, polyvinyl chloride and cellulose acetate, the latterresin-based films having previously been rendered conductive orsemi-conductive. The actual application of these photoconductive systemsto the selected substrate may be accomplished by the use of anytechnique which is capable of depositing a continuous film on thesurface thereof. Thus, among the various methods of application whichmay be utilized, one may list wire wound land grooved rod applicaors, aswell as air knife, trailing blade, gravure, reverse and direct rollcoaters. Typical coating weights may range from about 8 to 30 pounds per3000 square feet of substrate.

Following their application, the photoconductive coating systems aredried by any convenient means as, for example, by the use of forced airoven drying, infra-red or radiant heat drying. Here again, such dryingmethods are well known and the practitioner may employ the drying meansbest suited to his particular needs in light of the equipment which isavailable.

In order to demonstrate the excellent photoconductive propertiesexhibited by the coating systems of this invention, the tests describedhereinbelow may be used. In each instance, these tests were conducted inan environment wherein the relative humidity was at a level of 50%.

Charge Acceptance: The selected photoconductive coating system isapplied onto a paper substrate in a coating weight of 14 pounds per 3000square feet of paper and then dried. Thereafter, the coated paper iscondltioned, in the absence of light, for a period of 24 hours whereuponit is exposed, while still in the dark, to an electrostatic chargingunit for a period of 7 seconds. The surface charge which is thusimparted to the coated paper 1s then measured by means of anelectrostatic probe.

Dark Decay Rate: Continuing the procedure of the Charge Acceptance test,immediately after removlng the charging unit and measuring the depositedsurface charge, the electrostatic probe is utilized to measure the rateat which the charge dissipates from the surface of the coated paper bymeasuring the surface charge for a period of seconds. Needless to say,photoconductive systems which exhibit a low dark decay rate, 1.e. 1n therange of about 2 to 8 volts/second, are preferred for use inelectrophotographic operations.

Light Decay Rate: On completing the Dark Decay Rate the electrostaticprobe is utilized to measure the rate at which the charge dissipatesfrom the surface of the coated paper when it is exposed to a lighthaving an intensity of 16 foot-candles. The rapidly decreasing voltageis mechanically recorded on a revolving drum recorder the speed of whichis held constant for a series of samples. The light decay rate isexpressed in terms of the angle at the abscissa which is obtained whenthe light decay rate, as expressed in terms of the voltage, is plottedagainst time where time is plotted along the abscissa and voltage isplotted along the ordinate. Thus, a sample which had an instantaneousdischarge would, of course, display a 90 angle. Inasmuch as the speed ofthe recording drum itself affects the plot of the discharge curve andthereby the angle obtained with respect to time, the Light Decay Rate ofa particular sample is a value which is relative to a control samplewhich is run under identical conditions.

The following examples will fully describe embodiment of this invention.All parts given are by weight unless otherwise noted.

EXAMPLE I This example describes the synthesis of 1:1 (mole) mixture ofa new bromine-containing monomer, ethyleneglycol monomaleate 2carbobutoxy-3,4,5,6-tetrabromobenzoate, and monobutyl maleate.

Tetrabromophthalic anhydride (232.0 parts), n-butanol (72 parts), andsodium acetate (1.07 parts) 'were charged into a closed stainless steelreactor equipped with a mechanical stirrer, a thermometer and a gasinlet tube. The reactants were heated to 95 C. and maintained at thistemperature for 2 hours to form 1:1 (mole) of monobutyltetrabromophthalate and n-butanol which had an acid number of 94.3. Theinfrared spectrum of the mixture showed complete disappearance ofanhydride absorption bands at 5.4 and 5.6 microns. The temperature ofthe reactor was then lowered to 70-75 C. and thereafter tetramethylammonium chloride (2.7 parts) was charged into the reactor. Thereafterethylene oxide was added slowly through the gas inlet tube over a periodof 2 hours and the reaction was continued for an additional hour at thesame temperature. The product which was a 1:1 (mole) mixture of butylhydroxyethyl tetrabromophthalate and n-butanol, showed an acid number of0.1. Finally, maleic anhydride (98 parts) was added to the mixture andtemperature was raised to 80 C. The reaction was allowed to proceed for2 hours. The completion of the reaction was followed by thedisappearance of anhydride absorption bands of maleic anhydride at 5.4and 5.6 microns. The final product, which was obtained as an almostcolorless viscous liquid, had an acid number of and contained 37.2% ofbromine.

EMMPLE II This example describes the synthesis of the pure brominecontaining monomer, ethylene glycol monomaleate-2-carboethoxy-3,5,6-tetrabromobenzoate.

Step I.Synthesis of ethyl hydroxyethyl tetrabromophthalate intermediateTetrabromophthalic anhydride (580 parts), ethanol (143.5 parts), andsodium acetate (2.66 parts) were charged into the same type of reactoras described in Example I and heated to 80 C. for 1 /2 hours. The acidnumber of the product, which was a 1:1.25 (mole) mixture of monoethyltetrabromophthalate and excess ethanol, was 96.2. The temperature of thereactor was lowered to 70 C. and thereafter tetramethylammonium chloride(5.86 parts) was charged into the reactor. Thereafter ethylene oxide(73.2 parts) was added slowly through the gas inlet tube over 2 hours.The reaction was continued for an additional hour for completion. Theacid number of the product which was a 111.25 (mole) mixture of ethylhydroxyethyl tetrabromophthalate and excess ethanol, was 0.2. Excessethanol was then removed by washing with water and the product, ethylhydroxyethyl tetrabomophthalate, was obtained as a white powder afterfiltration and drying at 40 C. under vacuum for 24 hours. The acidnumber and melting point of the product were 0.173 and 118-121 C.respectively.

Step II.-Reaction of above intermediate with maleic anhydride Ethylhydroxyethyl tetrabromophthalate (138.5 parts) and maleic anhydride(24.5 parts) were charged into a multiple neck flask fitted with aglass-sealed stirrer, a thermometer and a condenser fitted with a dryingtube.

9 Reactants were heated to 85-90 C. and allowed to react at thistemperature for about 6 hours. The viscous product was then crystallizedfrom vinyl acetate as a white powder having a M.P. 80-84 C., and acidnumber 88.0, and containing 49.8% of bromine.

EXAMPLE III This example describes the synthesis of pure ethyleneglycolmonomaleate 2 carbobutoxy-3,4,5,6-tetrabromobenzoate.

Step I.Synthesis of butyl hydroxethyl maleate The synthesis of the aboveintermediate mixed with nbutanol in 1:1 mole ratio has already beendescribed in Example I. Unreacted n-butanol was removed by washing thebenzene solution of the mixture with water 4 to 5 times. The washedmaterial was dried over anhydrous sodium sulfate, filtered, and benzenesolvent was stripped 01? under vacuum at 4050 C. The intermediate, butylhydroxyethyl maleate, was obtained as a colorless viscous liquid havingan acid number zero.

Step II.Reaction of butyl hydroxyethyl tetrabromophthalate with maleicanhydride Butyl hydroxyethyl tetrabromophthalate (198 parts), maleicanhydride (32.65 parts) and sodium acetate (2.3 parts) were charged intothe same type of flask as used in Step II of Example II. Reactants wereheated to 80 C. and allowed to react at this temperature for about 6 /2hours. The product was obtained as a viscous mass having an acid number88.8, which is slightly higher than the theoretical value, andcontaining 46.5% of bromine.

EXAMPLE IV This example describes the synthesis ofmono-2,4,6-tribromophenoxyethyl maelate.

Step I.Synthesis of 2,4,6-tribromophenoxy ethanol intermediate2,4,6-tribromophenol (94.9 parts), ethylene oxide (14.7 parts) andtetramethylammonium chloride (2.0 parts) were charged into the same typeof reactor as described in Example I. Reactants were heated to 95-100 C.over 2% hours and allowed to react at this temperature for an additional4% hours for the completion of reaction. The product was then dissolvedin benzene, washed with water three times, dried with anhydrous sodiumsulfate, filtered, and benzene stripped off under vacuum at 40 C. Thefinal product was a slightly colored pasty material having a hydroxylnumber of 150.

Step II.Reaction of above intermediate with maleic anhydride2,4,6-tribromophenoxy ethanol (37.5 parts), maleic anhydride (9.8parts), and triethylamine (0.1 part) were charged into the same type offlask as described in Step II of Example II. Reactants were then heatedto 80 C. and allowed to react for about 9 hours. The product was thendissolved in toluene, washed with water 4 times, dried over anhydroussodium sulfate, filtered, and toluene stripped off under vacuum at 4050C. The final monomer was obtained as a slightly colored viscous materialhaving an acid number 110 and containing 51.0% of bromine.

When the dibromo compound is used parallel results are obtained.

EXAMPLE V This example describes the synthesis of 2,3-dibromoallylmaleate.

Step I.Synthesis of 2,3-dibromoallyl alcohol Propargyl alcohol (42parts) was charged into a multiple neck flask fitted with a glass-sealedstirrer, a dropping funnel, a thermometer and a condenser fitted with adrying tube. Bromine (120 parts) dissolved in methylene chloride parts)was added slowly over a period of 2 hours while the mixture was kept at5 to 8 C. The reaction was allowed to continue for an additional hour atthe same temperature. Methylene chloride was then stripped oif underreduced pressure at 40 C. and the crude alcohol thus obtained wasdistilled under vacuum (10 mm.) at 97.5 to C. The N was 1.5789.

Step II.-Reaction of 2,3-dibromoallyl alcohol with maleic anhydride2,3-dibromoallyl alcohol (21.6 parts), maleic anhydride (12.25 parts)and triethylamine (0.05 part) were charged into a flask fitted with aglass-sealed stirrer, a thermometer and a condenser fitted with a dryingtube. The reaction mixture was heated at 94-97 C. for 5 hours. Theproduct was then dissolved in toluene 100 parts), washed 4 times withwater, dried over anhydrous sodium sulfate, filtered, and toluenestripped off under vacuum at 40 to 50 C. The final product was a lowmelting white solid having an acid number 170. The acid number wasslightly lower than the theoretical value (178.6). The product contained51.5% bromine.

EXAMPLE VI This example describes the synthesis of 2,3-dibromoally1methacrylate.

2,3-dibromoallyl alcohol (100 parts), methacrylic acid (86 parts),concentrated sulfuric acid (1.94 parts), methoxy hydroquinone (1.94parts), and toluene (50 parts) were charged into a flask fitted with aglass-sealed stirrer, a thermometer, and a Dean and Stark apparatusfitted with a condenser. The mixture was heated to reflux and thetheoretical amount (8.3 ml.) of water was collected over a period of 3hours. The mixture was then diluted with ether (200 parts), washed withwater and dilute (3%) sodium hydroxide solution to remove excessmethacrylic acid and sulfuric acid, dried over anhydrous sodium sulfate,filtered and solvent stripped off. The fraction was collected at 65-83.5C. at 1.25-1.88 mm. Hg. The monomer was characterized by infraredspectrum and saponification measurements and was found to be 99% pure.It contained 41.7% bromine.

EXAMPLE VII This example described the synthesis of methacryloxyethylmono-tetrabromophthalate.

Tetrabromophthalic anhydride (139 parts), 2-hydroxyethyl methacrylate(64.4 parts), and triethylamine (5.4 parts) were charged into a flaskfitted with a glass-sealed stirrer, a thermometer and a condenser fittedwith a drying tube. The mixture was heated to 8085 C. and the reactionallowed to continue for 6 hours. The mixture was cooled and diluted withtoluene (200 parts), washed three times with water, dried over sodiumsulfate, filtered and stripped of toluene under vacuum at 40-50 C. usingair bleed as an inhibitor. The monomer was recovered as a viscous masswhich on standing for a week solidified. The M.P. and acid number of thesolid monomer were 220-225 C. and 99 respectively. It contained 52.8%bromine.

EXAMPLES VIII-XII These examples describe the synthesis of additionalbromine containing monomers such as mono-2-bromoethyl maleate (ExampleVIII), 2-bromoethyl methacrylate (Example IX), mono-2,3-dibromopropylmaleate (Example X), 2,3-dibromopropyl methacrylate (Example XI) and2,3-dibromopropyl acrylate (Example XII). In Examples VII and X themonomer was purified by washing with heptane; in Examples IX, XI, andX11 the monomer was purified by distillation under vacuum. The synthesesare summarized in Table I.

TABLE 1 Ingredients VIII 2-bromoethanol (parts) 65. 6

2,3-dibromopropanol (parts) Maleic anhydride (parts) 40. 9 Methylmethacrylate (parts) Methacrylic acid arts) Acrylic acid (parts Methoxyhydroquinone gparts) N-phenyl-2-naphthylamine (parts) Benzene (parts)Aluminum isopropoxide (parts) Sulfuric acid (parts) Trlethylamine(parts) Reaction time (hours).

Reaction temperature Yield (percent) Bromine (percent) Melting point C.)Boiling point 0.) Acid number 1 At 0.5 mm. Hg. 2 At to mm. Hg.

EXAMPLE XIII This example describes the synthesis of3-bromo-2-hydroxypropyl acrylate.

Acrylic acid (72 parts) and tetramethyl ammonium chloride (2.9 parts)were charged into a flask fitted with a glass-sealed stirrer, athermometer, a dropping funnel and a condenser fitted with a dryingtube. Epibromohydrin (137 parts) was slowly added from the droppingfunnel over a period of 5 hours while the reaction was continued for anadditional hour after the slow addition. The progress of the reactionwas followed by the disappearance of acidic carbonyl absorption band andat the same time app'arance of ester carbonyl absorption band in theinfrared spectrum. The acid number of the final product was about 0.5and bromine content 79.9%.

EXAMPLE XIV This example describes the synthesis of a 1:1 (mole) mixtureof propyleneglycol monomaIeate-Z-carbobutoxy- 3,4,5,6-tetrabromobenzoateand monobutyl maleate.

The process of synthesis of the above monomer was similar to thatdescribed in Example I, except that propylene oxide (62.5 parts) wasused instead of ethyleneoxide. The mixed monomer was obtained as aviscous product having an acid number of 130 and a bromine content of37.1%.

EXAMPLE XV This example illustrates the preparation of a randominterpolymer of styrene, di-butylfumarate (DBF), and the A and B werecharged into a reactor equipped with a mechanical stirrer, nitrogensparger, addition funnel and condenser. After degassing and spargingwith nitrogen six times, the system was maintained under nitrogenatmosphere and the temperature of the mixture was raised slowly over aperiod of 1% hours at 8590 C. and held there for an hour. Solution C wasadded in four equal portions at one hour intervals. When the lastportion had been added, the reaction was allowed to proceed twoadditional hours at 95 C., after which time D was added and the productcooled to room temperature. Conversion-98%; color-colorless, slightlyhazy; acid number25 and I.V. in toluene0.12 dl./ g.

EXAMPLE XVI This example illustrates the preparation of a typicalphotoconductive coating system of this invention as well as theexcellent properties resulting from the use thereof on a solidsubstrate.

Thus, 10.2 parts of a toluene solution containing 49.0% by weight of therandom interpolymer described in Example XIV hereinabo-ve, were mixedwith 49.8 parts of toluene and 40.0 parts of a finely divided,photoconductive zinc oxide. (1:1 mixture of St. Joe #325-PC and 340-PC,St. Joseph Lead Co.) The resulting suspension was subjected to grindingin a porcelain ball mill for a period of 3 hours so as to reduce theparticle size of the mixture to within the range of from 4.5 to 5.5 onthe Hegman scale. Thereafter, 0.9 part, by weight, of a dye sensitizermixture comprising 1%, by weight, of disodium fluorescein, 1%, byweight, of bromophenol blue and 1%, by weight, of erichrome blackdissolved in methanol were intimately dispersed in the mix.

The resulting photoconductive coating system, which had a total solidscontent of 45%, by weight, was then subjected to the Charge Acceptance,Dark Decay Rate and Light Decay tests as described hereinabove, whereinit exhibited a charge acceptance of 470 volts, a dark decay rate of 5volts/second and a light decay angle of as compared to a commercialphotoconductive coating system which had a charge acceptance of 390volts, a dirlrsdecay rate of 9 volts/ second and a light decay angle 0These results clearly indicate that this photoconductive coating systemhas the capability of accepting substantially more charge, retainingmore of the accepted charge for a period of time suflicient to fix animage created thereon and discharging the charge faster on exposure tolight than the corresponding commercial photoconductive system.

EXAMPLE XVII This example illustrates the preparation of additionalrandom interpolymers (A to 0) used as binders in the photoconductivecoating systems typical of the novel compositions of this invention. Thesyntheses are summarized in Table II. The following abbreviations areused:

St-Styrene MEM-Monoethyl maleate DBF-Dibutyl fumarate VA-Vinyl acetateDBM-Dibutyl maleate EA-Ethyl acrylate MBMMonobutyl maleate Each of theresulting bromine containing interpolymers as well as the controlcommercial polymer system which contains styrene, 'dibutyl fumarate andmono-butyl maleate was tested as a binder in a photoconductive coatingcomposition" containing the same ingredients as described in Example XVIexcept that different zinc oxide (Green Seal 8 supplied by the NewJersey Zinc Co.) was used.

trical properties. As a matter of fact other electrical properties suchas, dark decay rate and light decay rate, are improved. 'High chargeacceptance will allow cutting down the coating weight of papermaintaining the charge acceptance of the coated paper at the same levelas current The p1gment to man solids who was mamtamed at 8:1 commericalpaper. in all cases, and all electrical measurements were carried Insummary, this invention provides novel bromineout m a controlled roommaintained at 50% relative containing monomers and novel and improvedpolymeric hum1d1ty at 25 C. in Table III the results obtained uponbinders for electrophotographic compositions derived from subjecting theabove photoconductive coating composition 10 these monomers. v to theCharge Acceptance, Dark Decay Rate" and Variations may be made inmaterials, proportions, and Light Decay Rate test procedures describedhereinabove procedures without departing from the scope of this in aresummarized. vention.

TABLE II Interpolymers A B c D E F G H 1 I K L M N Ingredients:

ST (parts) 33.8 67.6 67.6 83.8 67.6 33.8 67.6 13.5 67.6 91 33.8 33.820.8 DBll\. 4 19m) 42.8 85.5 85.5 42.7 85.5 38.5 85.5 17.1 85.5 85.5 m28.5 42.8

p MBM (parts) 5.4 10.8 10.8 2.4 10.8 MEM (parts) 5. 3 Monomer ofExample:

I (parts) 27.9 (1p 19.7 19.7 XI 1 (parts) 16.7 v (parts)- 39.3

(parts)- 16.0 11 (parts). 21.3 18.0 16.1 30.1 XI (parts)- 17.9 IX(parts) 12. 1 VII (parts) 7.4 x1v arts) 52.5 51.3 VA (partsyn V 33.5 EA(parts) 46. 9 Solvent (parts) 98.0 181.0 183.6 96.2 192.4 95.2 177.540.2 205.6 227.8 80.8 65.9 91.0 98 88.1 Benzoyl peroxide (parts). 3.05.4 5.5 2.9 5.7 2.8 5.4 1.2 6.16 6.81 0.66 0.66 0. 68 2.93 Temperature,85-90 85-90 85-90 85-90 85-90 85-90 85-90 95-90 85-90 85-90 72-76 72-76-90 85-90 85-90 Time (hours) 6.3 6.0 6.0 6.0 3.5 5.0 5.9 5.5 7% 7 7 5%5.5 6 6 Percent convers1on 95.7 98.7 100.0 100.0 92.0 95.0 97.8 100 97.697.3 90 96 98 98.2 100 Percentbromme 7.3 5.4 5.4 10.4 10.4 5.3 3.6 9.99.6 8.3 17.1 13.7 11.0 8.9 29 Acid numb 33.8 38.7 38.2 36.4 36.5 37.114.1 33.8 34.1 26.9 38.7 36.7 61.1 1v. (dl./g.) 1n toluen 0.09 0.11 0.070. 07 0.10 o. 11 0.12 0.11 0.12 0.11 0.14 0.14 0.08 0.09 0.10

1 Toluene was the solvent in all cases except K and 0; in K a mixturemixture of ethyl acetate (15 parts) and toluene (73.1 parts) was used.of ethyl acetate (14.5 parts) and toluene (66.5 parts) was used; in 0 a.t-Butyl peroctoate was used mstead of benzoyl peroxide.

TABLE In What is claimed is:

1. A bromine-containing, film forming interpolymer 35; 53; consistingessentially of residues derived from at least one Charge rate ratebromine-containing monomer selected from the group of Interpolymerixifii? 355 99%; compounds corresponding to the general formulas 400 108b (a) CH-C o OCH1C=CHBr 380 5 8o a a Y Br 480 8 85 (b) 440 7 85 BrCOO-R: 440 6 80 0 380 10 75 6 g 430 8 80 Br coo-car H0 -CH=CIE[COOH 37010 75 528 13 $2 500 5 83 Br R1 0 490 6 85 I l] 420 10 7o Br 0-CH1 HOCH=CHCO0H 550 10 75 580 6 80 r 500 12 (d) 0 400 10 76 12BrQO-CH1(IJHOii-CH=CHC00H r B1 EXAMPLE XVIII 60 wherem This exampleshows the preparat1on of a random 1nter- R =-H, CH polymer containing4-bromostyrene, dibutyl fumarate, R 1k 1 di l h i 1 to 4 carbon ato s,and monobutyl maleate, and styrene.

A polymer was prepared by the procedure of Example Y=H, or CH1(J=CHBr XVusing a charge of 4-bromostyrene (14.2 parts), dibutyl fumarate (42.75parts), monobutyl maleate (10.75 parts), and styrene (26.7 parts). Thepolymerization was at least one ethylemcally unsaturated monomer wh1chdoes carried out at 8590 C. for 6 hours and yielded a poly- 110i 11ta111q mer having an acid number of 37.3 and an intrinsicvisbromlnli-contammgf film formmg 'p y cosity of 0.11 and containing6.6% bromine. When tested 60115180118 y of fesldues from at least (me asin Example XVII, the polymer of this example exhibit- K101101116!selectefl from the group 6011' ed properties superior to the Conn-o1 fExample XVIL mug of compounds correspondmg to the general for- From theabove results it is observed that all these mulas bromine containinginterpolymer systems ofier excellent 000-CH1C=CHBr charge acceptancewithout affecting adversely other elec- E R =alky1 radical having 1 to 4carbon atoms,

and at least one ethylenically unsaturated monomer which does notcontain bromine selected from the group of compounds corresponding tothe general formula 1,094,723 12/67 Great Britain 260-485 H JOSEPH L.SCHOFER,Primary Examiner C. A. HENDERSON, 5a., Assistant Examiner US.Cl. X.R.

96--1.5; 117l21; 26078.5 B, 78.5 UA

